Hydrogen Diving with Wet Mule John Dalla-Zuanna - FULL INTERVIEW .

All right guys, welcome back to this is part two of a two-part interview with John Dallazuana, Hall of Fame life member and inductee for over 45 plus years of the Cave Diving Association of Australia, amazing diver. He's helped out on some of the world's biggest dives that you've obviously seen with Richard Harris diving into those caves in New Zealand, just doing amazing stuff. He's got an amazing 3D software that he's helped develop and they go through and they video and build the 3D models of caves as well. John, thank you so much for coming back. It's a pleasure, let's do it. So John, I wanna kind of pick up where we left off and I wanna get a little more detailed. So let's get a little more detailed on the planning, how, this has to be an amazing amount of math. You start planning out an 800 foot dive and you've got 10 people that are doing, you know, surface support and diving support. How do you decide what gases to use and what depths you're gonna use for yourself? Well, there's obviously the two parts to that, that's the support divers and what they do as compared to what the Harry and Craig and Ho are doing at the cutting edge. Obviously Trimix is the big quest, but not only that, we are in a limited environment whereby weight and resources is to an extent limited. So we had to start thinking about simple things like back gases and all that. Obviously we're playing with green breathers, which is the most economical way of doing it. The early exploration done in say New Zealand with Pierce Resurgence was done on an open circuit. And obviously they were able to reach 100, 120 metres and got stuck in a particular area of the cave where they couldn't see their way on. And they obviously carried a lot of equipment to get to that point. And clearly exploration beyond that became onerous in terms of gear. So green breathers were the tool of choice clearly. And that back in the early or the late 2000, 2007, eight type era. But from there, we started looking at deeper dives and assembling a team of people that did deeper dives was sort of a little bit difficult initially because there weren't many people around doing that type of diving, 700 metre dives back in the 2006, seven, eight era. So finding the right team at that point was super interesting. And fortunately we're able to do that. And we were playing around with the deep wrecks around Australia at the time to do that. But our interest was cave diving. So with the green breathers, initially we were looking at setting up bailout scenarios and we were doing single person solo dives to get deeper into the cave. And you'd have the support team that'll go down to 150 ish. And then you had the backup diver who was able to do the 200 metre range and the cutting edge diver at the 200 metre as well. So we found that single diver was the way to go. Now, psychologically, that was quite a demand on people like Harry and Craig. And mind you, there's been some other divers that have joined us doing those sort of dives as well. Predominantly Harry and Craig in our team. And that started limiting our ability to go further because doing a solo dive, being in the water 12, 14 hours with sort of fairly primitive sort of habitats was starting to be very telltale. So we started looking at twin re-breathers at that point. And Harry and Craig were exploring ways of marrying two re-breathers so that they can actually cut down on the bailout scenario where we needed to string tanks all the way down the cave. So if we can minimise the number of bailout cylinders that we needed because we had twin re-breathers for each diver, then that obviously was the solution. However, once we started diving that 230-ish, 240 metre range, one of the huge things that started to become apparent is that arch enemy called the work of breathing. And the work of breathing started to be significant to the point that we had to be clear that the breathing re-breathers that we were using gave us the optimal less amount of work of breathing as possible. And we started to use 590 type mixes, 5% oxygen, 90% helium, and a little bit of nitrogen and started to push that 200 to 250 metre range. Now, overseas, there was a few other people doing the sub 250 metre at that time as well. So that was interesting. But what we started to find are two significant things. One is that the work of breathing increases because of the density of gas that we were using, that is the helium and the oxygen. And once you go below 200 metres with that sort of mixture of 490 or 590 type mixture, your gas density will be greater than what we call six grams per litre, do the maths. And six grams per litre is sort of a reasonably high level where you can cope reasonably well with the difficulty in breathing or the work of breathing. So if you go above six grams per litre, you'll start to go into laboured breathing. Soon as you got laboured breathing happening, you got the problem of carbon dioxide retention. And we start looking at the effects of carbon dioxide poisoning, so to speak. Even though the scrubbers are technically doing their job, but we need to be aware that anything denser than six grams per litre, we start going to trouble. So a 590 mixture is around about six grams per litre at 200 metre mark. When you go close to 300 metres, between 200 and 300 metres of depth, the density of that gas in a tri-mix of helium and oxygen, you have the situation where you're going close to eight or nine grams per litre of density. So you're way into the work of breathing, a high work of breathing scenario. Notwithstanding that, four or 5% oxygen will take you to a PPO2 of oxygen around 1.5, 1.6 easily. So you're going to have a high partial pressure of oxygen and you've got a high density of gas when you go deeper than 200 metres. And our videos of our boys, when they're in that 200, 250 metre, was demonstrating that they were starting to get shakes and things of that nature there. So we have a scenario of work of breathing. We can hear that and feel and sort of hear that heavy breathing, that laboured breathing. And at the same time, we start to see the shakes. And the shakes is actually the high pressure nervous syndrome, HPNS, that was starting to come in. So people who are doing these extreme dives have a very, very high tolerance to work of breathing, have a very, very high tolerance to the HPNS. And some have survived and some haven't. And consequently, those 250 metre plus divers are on that edge physiologically. And we are normal people. We're not those superhuman type people. And we recognise that. And we said, there's got to be a better system. So it was foolish for us to think that we could go to 250, 300 metres just like this in a cave because we're using Trimix and all that. And some people overseas did it. The rationale was knocking on the wrong door. And consequently, that needed a big think. And Richard Harris, with his medical background and interest and Craig as well, they started looking for solutions to this. And it was a collaboration with people like Michael Munduno, who brought together a team of people to start exploring what is the solution to cut down the work of breathing? What is the solution to knock down the HPNS sort of stuff? And we're saying, well, what is wrong with hydrogen as a gas? Obviously, it's a lighter gas. And can we use hydrogen to do the job of helium and get rid of a whole stack of things? So they started workshopping that as a theoretical model, unbeknownst to the working party, Harry had some very specific interest in actually trying it out and going through a whole stack of steps to see if it can be done safely. And that was the discussion that occurred about two years ago. The nexus of that was two years ago and we've evolved from there. Shall I continue? Oh, absolutely. So let's jump into a little bit. What are the significant hazards associated with using hydrogen as a diving gas, particularly like flammability? Well, exactly that. So basically, hydrogen is an extremely explosive gas when mixed with oxygen, stoichiometry, that's the word. Once you got more than 4% oxygen in the mix, hydrogen is super explosive. All it needs is a spark and it goes bang, literally goes bang. And the spark could come from a number of potential sources at the time. I mean, we're talking about a rebreather that's got a solenoid battery. We're talking about even the static friction of the counter lungs. If the counter lungs are dry, causing a static spark inside a hydrogen oxygen tank. It is clearly a dangerous gas to work with. And we have to do a decanting. So you've got adiabatic pressure when you turn the valves off. You've got boosting, which is something that we didn't know about whether we could actually achieve that. We had notwithstanding other questions, decompression, adiabatic diffusion, there's a whole set of other things that we had to think about as possibilities, but we couldn't solve every problem. So Harry started experimenting initially. So the obvious question is, will it blow up? That's probably the most number one thing. And the way he did that was cunningly, he put some hydrogen in the cylinder, used the hydrogen as a diluent, had an oxygen cylinder with his rebreather, and he put his unit in a swimming pool. And basically the whole thing was submerged. If anything was gonna happen, it might blow upwards rather than sideways. And he tells the story that he had to wait for his wife to go and do some shopping, so she wasn't at home when he experimented with this in the backyard pool. But essentially, he then turned the unit on and let the solenoid actually fire away by its own accord, building up the partial pressure, set the PPO2 on the breather 0.7, and turned the unit on and watched it slowly inject the oxygen in the hydrogen sort of environment. And that was just a pure oxygen hydrogen environment test. And he thought, well, it didn't blow up the first time. And then he sort of carefully injected oxygen into the breather in the pool, and that seemed to work. So he was quite confident that he's got away with that at that point. And that was basically where he left that until we went to New Zealand and said we're going to do this. So once we got there, we had to boost hydrogen into its own bottle. So the basic concept was we used the standard trimix in our rebreather down to about 200 metres. And once we got to 200 metres, we set out obviously our PPO injector to 0.7, kept it as low as possible. We didn't want a high oxygen mix into the system. And by setting our injector down to 0.7 meant that we trickled the oxygen in slowly. You start off with a mixture of, again, 490 trimix of helium and oxygen or oxygen helium. And we were able to take that down. And his idea was that when you got to 200 metres, he would shut down the dil mix of helium and open up the oxygen mix and inject some, sorry, open up the hydrogen mix, which was a separate bottle. And he would do that by using a switch block that was plumbed into the system. So click the switch and hydrogen would now go in as a diluent. And then he would push the hydrogen into his lung and slowly breathe that out. Now, what that did was change the mixture to approximately 30% or 40% of hydrogen. Again, maybe 30, 40% of helium. And you had an oxygen amount of around about 3-ish percent. So we kept the oxygen below 4% as much as we can. So if we had the oxygen percentage in the mix less than 3%, that means that the PPO2 of oxygen at 200 metres would have been about 0.6 of a bar. So the oxygen was at a reasonably good amount to sustain the breather. The partial pressure of oxygen was low enough, but corresponding to that, we had about 3% of oxygen in the overall mix. You had about 30, 40% of helium, 30, 40% of hydrogen. So you have that blend. I think they coined it hydroliox as a mixture. But what that did was it kept the work of breathing between 200 metres and potentially 300 metres to under six grammes per litre. It kept the partial pressure of oxygen between 0.6 to 300 metres goes to about 0.9. And at the same time, it reduced the prevalence of high pressure nervous syndrome, remarkably, anecdotally, by looking at our videos. And what we were able to say is that the mixture worked. It was really difficult to be precise whether you're injecting 30 or 40% of hydrogen using this system, because as we're going down below 200 metres, Harry was injecting a bit of hydrogen into the system to add diluent to his depth so that he had his optimal breathing. And that mixture enabled him to kill the HPNS. His work of breathing felt really good. His PPO2 of oxygen was at the right sort of level and things worked really well. And he was very, very happy with the whole procedure. And he got to, I think, 235 metres before he decided to call it for that particular dial. So the experiment worked. So on the way back up, he would come back to 200 odd metres and then he would switch off the hydrogen and he would then start to add oxygen and helium into the mix by venting every oxygen I think it was every 10 breaths or every, probably every 10 breaths, I can't recall now. I think it was after every 10 breaths, he would vent out a load of hydrogen helium out and then he would inject the helium trimix back into the system. So by 150 metres, by the time he got to 150 metres, he was back onto normal trimix because he needed to plug in and get O2 into the system so that he can decompress more rapidly without penalising himself with multiple hours of decompression. So he was able to push up the O2 as he ascended, which he needed to do, and at the same time reduce the hydrogen out of the system. And at 150 metres, he was back to normal trimix and then continue this dive to the surface accordingly. So by doing that, we're able to use the hydrogen deep depths, get rid of it by the time I'm back to 150 and then finish the dive off normally. And we made the decision to follow the decompression procedure as if it was just a straight trimix dive as it was a normal helium dive. So we kept the same logistics with the computers to do our decompression as if the whole thing was done on trimix. And consequently, it worked. And as Harry keeps pointing out, n equals one. In other words, he successfully was able to do one dive in the whole system. So we're not advocating this as a success per se, but it's certainly in the right direction. And the whole bottom line here is now that we can start thinking about exploration at depth as opposed to plunging down, looking at the bottom, coming back up and surviving a 300 metre dive. That has been done, albeit not very often, but now we can actually do that and we can start considering, can we start doing exploration at depth? In other words, can we be functional? Before you start kicking at 250, 300 metres and the work of breathing skyrockets, the CO2 skyrockets and you've got yourself a situation which is probably extremely difficult to bail out of. So yeah, it opens the door to something new and this is something that we'll be looking at continuing over the next year or two. So when Harry first talked to you about this, what were your thoughts? Well, everyone had their different theories about whether hydrogen in the system hydrolyzes your blood system so it becomes acidic. We knew about the explosive factors and we knew about all of that sort of stuff there. But at the same time, I think all of us are not, what's the right way to put it? We're not sheep, we're sort of, we're rational human beings and we think about what each person is doing. And even the pressure, totally off topic, but even the pressure of having a filming crew looking at what you're doing and you're sort of saying, I'm focusing on the dive, I'm not focusing on the fact that I've got a camera guy beside me or something stupid like that. We had to argue over what is acceptable and what isn't. And consequently, we sat down and talked a lot about what to do, what the implications are of various things that might've occurred with the hydrogen steps. We understand that there were a number of people in the discussion team initially that threw this concept around. We had some pretty heavy type people discuss it. Some were pro, not that people were against it, but not many people knew that it was gonna be a practical thing as much as a theoretical discussion. But ultimately, there were a lot of serious thought being put behind what we were going to do. And yeah, when Harry and Craig put it all out on the table, this is how we're going to do it. Mind you, it was chosen that Harry did the dive and Craig would support him at that depth. So Craig stayed on the trimix. And that's one of the reasons why we were aiming just for the 230, 240 we were looking at. Again, I think I've mentioned previously, we do things in very small steps. Familiarity breeds safety. So we were very conscious of what was happening. I mean, we all hid behind the bushes when we started boosting. We all respected the fact that things could go south. And at the same time, we're very clear about what we will do and what we can do to a possible known extent. And yeah, we discussed. So we understood what they were doing, how we were doing it, and why we were doing the various steps. And we were geared up for that all the way through. And wouldn't we do it again? Of course we would, yeah, not a problem. So you've gone through, I guess one of my interesting questions is how hard is hydrogen to get? Oh, it's super easy, relatively easy here. We can order a bottle of hydrogen gas quite simply. It's used for instrumentation work. The valve setup is very simple. It's a left-hand thread rather than the standard right-hand thread. We can turn those adapters out fairly easily. So we can transfer from a bottle straight into another bottle or stick a booster onto it and pump it away. If the booster is oxygen clean, it works for hydrogen as well. It's no biggie. Hydrogen needs oxygen to blow, and oxygen seems to find its material through debris and things like that in order for it to burn. So if your gear is clean, and if it can boost oxygen, it'll boost hydrogen. So we were comfortable with it. We obviously made sure that we boosted slowly. We obviously made sure that we didn't have too much heat in the system as much as we could. So, you know, very slow boosting as opposed to fast boosting. And yeah, step by step. But we've ascertained that it can be decanted and boosted. We've made the comment that hydrogen is compatible with our CCR. We had a strategy to inject oxygen at 100% on the ascent phase by venting out the loop and getting it filled up with diluent, trimix diluent. We overcame the fact that we kept the decompression schedule the same as trimix. So we got rid of that phobia of whether or not it would be different. I think it was important that we kept a very low set point on the descent so that when we got to depth, we weren't dealing with high O2 at the time. So that worked out. There's a couple of those strategies that we thought about that we implemented that worked. And I think the accessibility of hydrogen was super easy. We could get it in New Zealand. We can get it in Australia. Wasn't an issue. And of course, the narcotic effect in the HPNS was something that anecdotally also was not present much better than previous dives. And Harry was very, very happy with that. And he's quite ecstatic about it. Yeah, so it worked. Right on. So you went to the initial testing where Harry didn't blow up his house, which we're very glad about that. Downed out apparently with a credit card, you can buy your own hydrogen. Took it out, you dove it now. So now, what have you learned since starting this project that you didn't think about before? I think there's a whole stack of issues that we don't know at this stage. And we're not clear whether decompression is as easy as tri-mix and hydrolox, whatever you call it. The hydrogen and oxygen mix is the same. Obviously things with like inner ear decompression and also inner ear BCS is an area that we don't know if hydrogen is going to create issues like tri-mix does. Counter the fusion, is it an issue? And please, we revert back to what Harry keeps saying, this is N equals one. In other words, we've done one dive with it at this point. So all the ducks lined up and they worked well for that particular dive. We certainly will look at repeating a whole stack of things over the next 12 months and working out where we're going to take this next. But there will be more dives. There's no doubt about it. Having said that, as I said, is decompression as simple as follow the tri-mix decompression model? Is the counter diffusion of switching from a hydrogen to a helium to whatever hydro-free mix, is that going to cause any effects? We've got a super light gas hydrogen. So thermal considerations is something that's going to be huge. We weren't, or Harry wasn't on hydrogen for that long, a period in the overall scheme of things. But if you are starting to do time on hydrogen, how much body heat, thermal stress are we going to be putting ourselves under in waters that are cold? The pierce is six degrees. I forgot to mention that at the beginning. So we're obviously using heated undergarments for certain parts of it and so forth. Scrubber duration, is that going to be affected? So when we start doing these longer dives, what's the scrubber going to do? There's a couple of big questions that we don't know in order to move this into an exploration stage. And that's, we're not doing the hydrogen for depth. People do, if you're going to do that, they might as well do it in the habitat or a bell of some description if you want to say how you breathe hydrogen at depth. But if you're going to do exploration, environment will stop to begin with, let alone playing around with the hydrogen gas. So I think we need a few more hydrogen dives before we start letting loose on the horizontal rather than just up and down. But anyway, that's the next phase. I can't imagine that one dive isn't a good control group. Well, it isn't. We'll just tell the story of the first one and then hopefully we're going to be telling more stories about number two, three, four and so forth. But yeah, no, seriously, the biggest challenge was the initial step. And clearly, yeah, someone had to do it and Harry put his hand up for it. And consequently, we were there for him and it worked. It worked successfully. But there are a lot of unknown questions that need dealing with. And we just can't keep going forwards with our head in the sand and say, it'll be right, mate, don't worry, it'll be right. It can't be that easy. It needs to do it. So whether we do longer dives on a single bounce and not do exploration, just so that we can start cutting out those other effects or yeah, basically that's where I think we'll be doing, spending our time in the next couple of dives, just doing single dives whereby we extend our time with the gas and then we start thinking about exploration down the track. Yeah, go on. So John, just a few more questions. So you go down some of these depths as a support diver, 150 metres. The average agency has their maximum certification to 300 metres. So you're sort of going up 50, 100 metres past where most people are ever getting certified to. So as you do get down to these deep marks, tell us about how that feels at 150 metres just to hang out and support. Well, it's a good question. It's certainly a very quiet place. I mean, you become very introspective, it's the wrong word. When I'm there, I sort of, I started doing some mapping at between 100, 120 metres on certain cave beaches and so forth. And you can sort of, you really feel that quietness, isolation, but it's not a terrifying isolation, but it's, you know that it's a very still place. It's a very quiet and your senses are really tuned to the max whereby you can hear yourself breathing, you can hear the machinery. I won't, I know people have reported and I have tasted, there's a metallic taste in your mouth or something like that. But you sort of are very, very aware that you are isolated. And I don't mean that, again, in a negative way. It's that solitude that you get. You can think clearly, that's the important thing. With Trimix, the right Trimix, you can clearly see things. You're not blurred, you're not suffering narcosis. You're very focused in what you're doing. But one thing that really, really builds up in the back of your head is the time that you are every minute. You know that there's a 30 minute sort of, the compression stop behind you. So even though you are enjoying where you are because it is quite a mystical place, yeah, you're very conscious of the fact that as every minute goes by, you've got a penalty, a decompression penalty that you have to do. The upper habitats are really good because you can stretch out, but the lower habitats are really boxes. It's a pain to sort of sit in there and I might throw a video on there of Harry and Craig in a little box at some stage. And you can see that it's just an uninviting environment. You have to suffer literally for a couple of hours to get out of that box into the next habitat. But knowing that that penalty is there really is the part that knocks you around the most, for me anyway. So love being at that depth, love the serenity, love the sight that I see when I'm down there. But then, I was running around in Kidja Blue at 120, zooming from one edge of the cave to the other and all that in nice warm water. And then I came up and realised I had nine hours of decompression to do. And that was in water, fortunately it was warm, but I had to write notes and send up to people to send me down another wetsuit, which I put on underwater at my deco stop so I could stay warm. And the jelly babies would come down so you can chew on those things. And chewing on a rebreather is quite different than chewing on a regulator. And it's weird, but it's another art. And so the penalty that you have to go through is what I dread. And at my age, nine hours, you become more than a prune in the water if you're sort of soaking in that. But, and the habitats as well. So that's the part that I dislike the most. But the depth down there, the right gas mix, it is really, it's another world, it's different. But yeah, but we were doing these dives before the agencies started talking about 100 metre limits or, you know, we had tickets that says generic CCR, not 100 metre CCR and things like that. So that was the other thing. The different rebreathers that we were using, initially the home builds all the way through to the more, what do you call, retail ones. And they're sort of, they have evolved, obviously. And things are different today than they were before. But we were making our own catalogs and hoping that the seams hold and things like that initially. But anyway, we learnt a lot, but it's not as easy as just getting a CCR ticket and just going from there. That's what I said before, you know, sort of experience breeds safety. And yeah, the more you do it, the more comfortable you become. But not complacent, that's another word, no. But yeah, I like the deep diving. I like the serenity and it gives you access to places that few people have been to before. So what advice would you give somebody that's getting ready to head into advanced Trimex or into CCR? Well, I think getting a group or a team together really helps support yourselves in that progression. So a person that goes off to get a ticket and he's on his little lonesome, does a course, ends up doing a wall, some sort of a resort and hits the 100 metres, comes back and he's got a CCR ticket. Good start, good start, at least the training is there. But unless you get like-minded people together, unless you get like-minded people together, it is super hard to continue diving deep. Even if you have one buddy and the two of you are doing Trimex dives to 100 metres, that is not right in a sense. You need support. Simple, like if you're doing an open water dive on a wreck or something, 100 metres, you are carrying a shitload of bailout bottles if you're going to do a single breather and it's a logistic nightmare to manage all your equipment. It's doable, but it isn't fun when you're carrying around three or four cylinders as well as a breather. Whereas if you have support divers, you have shot lines, you have deco stations, you have a system in place, then it becomes safer to do it that way. So my recommendation is get yourself a team of people or get involved with people who are doing these sort of dives and there's a number of them in different places that I've got projects on and get involved. And yeah, if you have to start as a support diver first, that's where you should start. And then from there, you'll be progressively getting deeper and into what you ultimately want to be as being a bottom diver, if I can put it as bluntly as that. But having said that, I think a team of people is where you should aim to be if you're going to think about doing 100 metres, some 100 metre dives, be it a wreck or be it a cave. If you're going to do it on your own, I think you're knocking in the wrong place. But, and having a team of people means that you'll be supporting each other and everyone will work to the strength of the team and move progressively. But if you have the one man hero and a support team that does it, again, I dislike that model intensely. But yeah, so get yourself involved with a team of people that are like-minded or are doing the type of dives that you would like to be doing and put your hand up and say, can I help? Can I do something? Soon as that boy comes up, that's in a different colour to the one that you're doing the safety stop with, go down with the extra cylinder. Are you okay? What do you need? That's the sort of support you start off with and then work your way from there. Gotcha. No matter how much your ticket is or what your ticket is, start somewhere and take your steps slowly. Well, John, thank you. What's next? What's the next dive for John? Good question. I think the next ones that I'd be, that we're aiming for, the team's got some projects on which I won't do in January. I think they're doing China. That might be a scoop and so forth. But I think I'm going to be focusing on some caves in the Malabar, in the Central Australia part, which are just starting to break open in terms of exploration. And they're shallow dives. 15, 20 metre sort of dives, but they do extend 8, 10, 12 kilometres or more. And there's a couple of caves which are starting to show a lot of promise. And one of my colleagues is joining me in a few weeks. And I think we'll head out west, as we say, and into the desert and start looking at some cave groveling. We use, for my shallow extended stuff, I use a sidewinder, a Rebreather. Comfortable with that. For the deeper stuff, I use the Meg, when you've got a bit more elbow room and all that. But groveling, the sidewinder, seems to slot me away around places quite nicely. Yeah, so cave diving for sure. I do have a bucket list of going back to Italy next year. And go to one of my favourite points, the cave called Fontanazzi, which is very, very close to my father's home birth town. That's why the cave diving is probably in the genes. But yeah, up in the northern part of Italy, there's a couple of beautiful caves that I've dived and I'd love to continue doing dives. Unfortunately, it's still cold water though. Six, quite high, six degrees. But anyway, it's nothing new. But yeah, that's the sort of stuff. So cave diving a fair bit is probably where I'll be for a while. And a bit of teaching the young kids at the university. That's another story altogether. Right on. Well, John, thank you for your time today. I appreciate you. Pleasure. Absolute pleasure. It's interesting talking about the past and the present. And yeah, when you look at it that way, there's quite a bit of stuff there, but I always like learning and I'm always interested in putting my hand up for something that's interesting like that. Why not? Right on. Well, guys, there you have it. John Dalla Zuana. Amazing. He's been on some of the biggest dives you can possibly imagine. Dabbled in the hydrolox. We'll come up with a cool term for that. Dabbled in hydrox, hydrogen diving. So we'll have to come up with a cool nickname term for that. But done some amazing dives. Dives with Richard Harris. We all know from the Thai rescue divers, the 806 foot dive in the New Zealand cave. Just amazing stuff. So just really thankful to have guys like John that are willing to share his knowledge with us. Again, my name is Richard Hatfield. I'm a technical dive instructor here in Idaho and in Florida teaching the masses how to go deeper, longer, and have more fun as well. If you like this kind of content, make sure to subscribe to our channel. Again, thank you, John. My pleasure. Thank you for having me.